TOPIC: Relevance Equation

I am trying to create a equation question, and for the question to take place, I want to make sure that none of the values are null before performing the calculation in the question. It would seem based upon the BMI example in the documentation that this should work.

Yet for some reason it is complaining about the originating curly brace, which I am assuming means that the error is probably somewhere else? Any help/ insight, or link to documentation would be greatly appreciated. I have scoured the wiki thus far with no concrete results.